The technology of fabricating semiconductor integrated circuits has advanced with regard to the number of transistors, capacitors and other electronic devices which can be fabricated on a single integrated circuit chip. This increasing level of integration has resulted in large part from a reduction in the minimum feature sizes of the integrated circuits and an increase in the number of layers which make up the integrated circuit. Today's design features, generally referred to as “sub-micron” have dropped below 0.25 microns. The manufacture of integrated circuit components having this reduced size has placed new demands on all aspects of their production including the removal of resists with chemical stripper solutions.
Semiconductor devices for semiconductor integrated circuits or liquid crystal displays are commonly produced by a process including the steps of coating a substrate with a polymeric resist composition; patterning the resist film by exposure to light and subsequent development; etching exposed portions of the substrate using the patterned resist film as a mask to form minute circuits; and removing the resist film from the inorganic substrate. Alternatively, after forming minute circuits, the resist film can be ashed and the remaining resist residues removed from the substrate. A superior stripper solution should quickly remove resist residues and materials at moderate to low temperatures, have an acceptable effect on the all exposed components, have a substantial capacity for the dissolved resist and/or post etch residue to forestall both the precipitation of solids and the early disposal of the stripper solution. A superior stripper solution should also quickly remove resist residues in a rework process without substrate damage. Finally, superior stripper solutions should exhibit minimal toxicity.
A variety of stripper solutions have been developed which have performed satisfactorily in the manufacture of the early semiconductor devices. A substantial number of the early stripper solutions have been strongly alkaline solutions. The use of the alkaline stripper solutions to manufacture microcircuits containing metals, particularly tungsten or copper and its alloys with aluminum, can lead to metal loss. Various forms of metal loss, such as for example corrosion whiskers, pitting and notching of metal lines, have been observed during the use of these alkaline strippers. In the case of tungsten and copper, corrosion can occur in the heated dry organic stripping composition mixtures with dissolved oxygen providing the cathodic reaction. Although such metal losses were acceptable in the manufacture of the early semiconductor devices, devices having sub-micron components cannot tolerate such metal losses.
Efforts have been made to reduce the loss of metal during the fabrication of semiconductor devices by utilizing stripper solutions containing a variety of corrosion inhibitors. U.S. Pat. Nos. 6,276,372; 6,221,818; and 6,187,730 teach the use of a variety of gallic compounds which function as corrosion inhibitors in stripper solutions. U.S. Pat. Nos. 6,156,661 and 5,981,454 teach the use of an organic acid as a corrosion inhibitor in stripper solutions. U.S. Pat. Nos. 6,140,287; 6,000,411; and 6,110,881 teach the use of chelating agents as corrosion inhibitors in stripper solutions. U.S. Pat. Nos. 5,902,780; 5,672,577; and 5,482,566 teach the use of dihydroxybenzene chelating agents as corrosion inhibitors in stripper solutions. U.S. Pat. No. 5,997,658 teaches the use of benzotriazole as a corrosion inhibitor in stripper solutions. U.S. Pat. No. 5,928,430 teaches the use of a gallic acid as a corrosion inhibitor in stripper solutions. U.S. Pat. No. 5,419,779 teaches the use of catechol, pyrogallol, anthranilic acid, gallic acid, and gallic ester as corrosion inhibitors in stripper solutions.
The corrosion inhibitors used thus far generally have a number of drawbacks which can include the following: (a) they are organic compounds not easily removed with a water rinse; (b) substantial quantities of the inhibitors are required and can affect the solution's stripping abilities; (c) inhibitors having chelating properties can adhere to metal and other component surfaces and interfere with performance; and (d) a component's toxicity and lack of biodegradability can make exposure to solutions undesirable and disposal of spent stripper solutions more difficult.
What is needed is a stripper solution containing a component which: (a) can, at very low levels, prevent the dissolution of metals and their alloys, including copper and other metals used in the fabrication of semiconductor devices; (b) is compatible with the stripper solution and doesn't interfere with its operation; (c) can be easily rinsed from a semiconductor device with water and/or a water soluble alcohol, leaving no residues; and (d) has low toxicity and does not negatively impact the biodegradability of the spent stripper solution. This present disclosure addresses and resolves these needs.